1. Field of the Invention
The present invention is generally directed to semiconductor processing components, and processing techniques utilizing such components.
2. Description of the Related Art
In modern semiconductor processing, semiconductor wafers are processed through various stations or tools. Processing operations include, for example, high temperature processing such as diffusion, oxidation, ion implant, annealing, and deposition. In each process station or tool, great care is generally taken to minimize contamination of the semiconductor wafers with particles and/or foreign or unwanted species. The demand for ever increasing and more stringent clean standards is driven by numerous factors in the industry, including migration to even finer device sizes and circuit density per semiconductor die. Further, the price per semiconductor wafer continues to increase exponentially, as the sizes of semiconductor wafers continually increase. In this regard, currently the industry is transitioning to 300 mm from 200 mm wafers and the cost associated with such wafers has jumped considerably.
In light of the cost of semiconductor processing, the cost of raw materials including semiconductor wafers, and the electrical density associated with current and next generation semiconductor devices, there is an intense driving force to reduce contamination during processing. Once source of contamination is generally well understood and relates to particles generated in various deposition processes, including high temperature deposition. More particularly, thin films such as polysilicon, silicon nitride, and deposited silicon dioxide, are oftentimes deposited via chemical vapor deposition (CVD) processing, particularly including batch processing utilizing horizontal and vertical furnaces. Conventionally, quartz has been utilized for the material of choice for various components of such process tools, including wafer holders (horizontal wafer boats and vertical racks), baffles, internal liners, and process tubes. However, due to differences in thermal expansion between these quartz semiconductor processing components and the materials that are deposited, film stresses tend to develop during repeated heating and cooling cycles. These stresses increase in concert with an increase in thickness of the deposited material. Accordingly, after numerous processing cycles, a critical thickness is reached, the film stress exceeds the modulus of rupture of the deposited film, and cracks develop. The cracked film then typically delaminates from the semiconductor processing components, forming particles within the processing tool that contaminate processing and reduce die yield.
In light of the foregoing, it has been essential to take the tool offline and execute a clean after a specified number of processing cycles. Given the cost of semiconductor processing, tool downtime is very expensive, and re-qualification and recalibration procedures for getting the tool back online are oftentimes exacting and difficult to meet.
Current generation technology has focused on use of alternative materials to minimize the difference in thermal expansion coefficients between the semiconductor processing components and the deposited films, and accordingly reduce tool downtime and extend cleaning intervals. In this regard, introduction and widespread use of silicon carbide-based semiconductor processing components has been successful, due largely to the better match in thermal expansion coefficients between these new generation processing components and the deposited films. Indeed, as compressive stresses in the deposited films have been attenuated by to such an extent that the maximum or critical thickness of the deposited film has increased by at least an order of magnitude. As such, significantly more process cycles may be repeated at a single tool prior to cleaning.
In addition to batch processing, semiconductor fabrication generally implements a series of single-wafer processes, oftentimes utilizing halogen plasmas for a variety of reasons such as etching. Halogen plasma application is a preferred method of etching metal and dielectric layers due to anisotropic etch characteristics. Due in part to widespread use of such aggressive plasmas in single-wafer processing, typically components are formed of anodized Al or aluminum oxide ceramics. However, the art has recognized generation of unacceptably high levels of Al metal, and AlF3 and AlCl3 particle contamination, originating from use of Al-containing compositions.
While introduction of silicon carbide-based semiconductor batch processing components has proven to be largely successful, a need continues to exist in the art for processing techniques and semiconductor processing components that even further reduce or enable reduction in contaminant levels and provide further improved semiconductor die yield. In addition, despite widespread use of anodized Al and aluminum oxide ceramics in single-wafer processing to withstand aggressive plasmas, a need continues to exist in the art for improved components, particularly components with attenuated metal and particle contamination.